Controlling mobile-device roaming

ABSTRACT

Media and systems for controlling roaming of a mobile device on a wireless-communications network are described. Wireless-communications systems along a coverage area border are designated as roaming border systems. A parameter value is communicated from wireless-communications systems of a home network to a mobile device. The parameter takes on a value indicating whether a mobile device is permitted to initiate a connection to a roaming network. A mobile device is restricted to use of home-network systems when a first parameter value is received. The mobile device is permitted to use home-network and roaming-network systems when a second parameter value is received. Thus, the mobile device can only roam when the second parameter value has been communicated thereto.

BACKGROUND

Roaming occurs in a wireless network when a mobile device, such as awireless phone, personal digital assistant (PDA), or other mobile deviceconnects to a network other than its home network. Manywireless-networks providers have contracted with each other to allow itscustomers to use the services of a second network for a fee (thoughoften transparent and unbeknownst to the mobile subscriber). By suchagreements, the wireless-network providers pay each other for theirsubscribers' usage of other wireless networks.

By negotiating agreements with other wireless-networks providers, agiven provider is able to offer continuity of service over a larger areawithout having to build out its own wireless network. But nevertheless,for a variety of reasons, a home carrier often would like for its usersto use its network.

SUMMARY

Embodiments of the invention generally relate to computer-readable mediaand systems to control roaming of a mobile device that is configured tocommunicate with a home network. A parameter value is communicated froma wireless-network communications system of a home network, such as acell sector, tower, or base station to a mobile device, such as awireless phone and is stored therein. The parameter value identifieswhether the system is a roaming border system. Roaming of the mobiledevice is thereby controlled by restricting the mobile device to use ofa home network system when the parameter value indicates that thewireless-communications network system from which the device receivedthe parameter value is not a roaming border system. The mobile device isenabled to connect to a wireless-communications network system of aroaming network when the parameter value indicates a roaming bordersystem. A prioritized list of authorized wireless-communications networksystems that the mobile device is authorized to use may also be providedto further control the mobile device's roaming when such is enabled.

This Summary was provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used in isolation as an aid in determining the scope of the claimedsubject matter.

BRIEF DESCRIPTION OF THE DRAWING

Illustrative embodiments of the invention are described in detail belowwith reference to the attached drawing figures, wherein:

FIG. 1 is an illustration of a wireless-network environment suitable foruse in implementing embodiments of the invention;

FIG. 2 is an illustration of a wireless-network communications towerdepicting a service area of an antenna according to an embodiment of theinvention;

FIG. 3A is a graphical representation of a map depicting a home-networkcoverage area of a wireless-network communications system according toan embodiment of the invention;

FIG. 3B is a graphical representation of a map depicting aroaming-network coverage area of a wireless-network communicationssystem according to an embodiment of the invention;

FIG. 3C is a graphical representation of a map depicting both ahome-network coverage area and a roaming-network coverage area ofwireless-network communications systems according to an embodiment ofthe invention;

FIG. 4 is a flow diagram depicting a method to enable awireless-telecommunications network to control a way that a mobiledevice selectively initiates communications with one of a home networkversus a second network according to an embodiment of the invention;

FIG. 5 is a graphical representation of a map depicting aroaming-enabled zone along a border of a home-network coverage area of awireless-network communications system according to an embodiment of theinvention;

FIG. 6 is a block diagram depicting a roaming control system forcontrolling a way that a mobile device selectively initiatescommunications with one of a home network versus a second networkaccording to an embodiment of the invention; and

FIG. 7 is a flow diagram depicting a method to enable awireless-telecommunications network to perform a method of controlling away that a mobile device selectively initiates communications with oneof a home network versus a second network according to an embodiment ofthe invention.

DETAILED DESCRIPTION

The subject matter of embodiments of the present invention is describedwith specificity herein to meet statutory requirements. But thedescription itself is not intended to necessarily limit the scope ofclaims. Rather, the claimed subject matter might be embodied in otherways to include different steps or combinations of steps similar to theones described in this document, in conjunction with other present orfuture technologies. Terms should not be interpreted as implying anyparticular order among or between various steps herein disclosed unlessand except when the order of individual steps is explicitly described.

Throughout this disclosure, several acronyms and shorthand notations areused to aid the understanding of certain concepts pertaining to theassociated system and services. These acronyms and shorthand notationsare intended to help provide an easy methodology of communicating theideas expressed herein and are not meant to limit the scope of thepresent invention. The following is a list of these acronyms:

PDA Personal Data Assistant SMS Short Message Service MMS MultimediaMessaging Service GSM Global System for Mobile communications UMTSUniversal Mobile Telecommunications System PCS Personal CommunicationService UMB Ultra Mobile Broadband RF Radio Frequency SID SystemIdentification NID Network Identification

Further, various technical terms are used throughout this description.An illustrative resource that fleshes out various aspects of these termscan be found in Newton's Telecom Dictionary by H. Newton, 24th Edition(2008).

Embodiments of the present invention may be embodied as, among otherthings: a method, system, or set of instructions embodied on one or morecomputer-readable media. Computer-readable media include both volatileand nonvolatile media, removable and non-removable media, andcontemplates media readable by a database, a switch, and various othernetwork devices. By way of example, and not limitation,computer-readable media comprise media implemented in any method ortechnology for storing information. Examples of stored informationinclude computer-useable instructions, data structures, program modules,and other data representations. Media examples include, but are notlimited to information-delivery media, random-access memory (RAM),read-only memory (ROM), electrically erasable programmable read-onlymemory (EEPROM), flash memory or other memory technology, compact discread-only memory (CD-ROM), digital versatile discs (DVD), holographicmedia or other optical disc storage, magnetic cassettes, magnetic tape,magnetic disk storage, and other magnetic storage devices. Thesetechnologies can store data momentarily, temporarily, or permanently.

Embodiments of the invention provide computer-implemented systems andcomputer-readable media for performing a method to control roaming of amobile device that is configured to communicate with a home network. Inone embodiment, computer-readable media having computer-executableinstructions embodied thereon that, when executed, enable awireless-telecommunications network to perform a method of controlling away that a mobile device selectively initiates communications with oneof a home network versus a second network is described. Roaming-bordercomponents providing signal coverage that collectively defines theborder of the home network are utilized. A parameter is communicated toa mobile device from a given roaming-border component. The parametertakes on a value that indicates that the mobile device is permitted toroam to the second network such that absent receiving the value, themobile device is not allowed to roam to the second network.

In another embodiment, a system for controlling a way that a mobiledevice selectively initiates communications with one of a home networkversus a second network is described. The system includes aparameter-receiving component, a system-identifying component, and aconnection-enabling component. The parameter-receiving component isconfigured to receive a parameter value from a home-network system. Theparameter takes on a first value that indicates that the mobile deviceis not permitted to roam on the second network, or a second value thatindicates that the mobile device is permitted to roam on the secondnetwork. The system-identifying component is configured to receiveidentification data communicated from the home network and the secondnetwork. The system-identifying component is also configured to comparethe received identification data to known identification data toidentify the communicating system. The connection-enabling component isconfigured to prevent communicating with the second network when thefirst parameter value is received and to enable communicating with thesecond network when the second parameter value is received.

In another embodiment, computer-readable media, havingcomputer-executable instructions embodied thereon that, when executed,enable a wireless telecommunications network to perform a method ofcontrolling a way that a mobile device selectively initiatescommunications with one of a home network versus a second network isdescribed. A preferred roaming list is provided including a prioritizedlist of, on a home network, non-roaming border cell sectors androaming-border cell sectors, and cell sectors on second networks that amobile device is authorized to utilize. The non-roaming border cellsectors are utilized to communicate a first parameter value in a firstsystem-parameters message to the mobile device. The first parametervalue indicates that the mobile device is not permitted to initiate aconnection with the second network cell sectors. The roaming-border cellsectors are utilized to communicate a second parameter value in a secondsystem-parameters message to the mobile device. The second parametervalue indicates that the mobile device is permitted to initiate aconnection with the second network cell sectors, whereby the mobiledevice is enabled to selectively initiate a connection based on thepreferred roaming list.

Roaming occurs when a user subscribed to a home network connects to anetwork other than the home network, hereinafter referred to as aroaming network or second network. A home network, as referred toherein, is descriptive of a wireless-telecommunications,wireless-communications network, or more simply a network to which auser is subscribed for wireless-communications service and is notintended to imply any relation to a user's home or dwelling. The termswireless-telecommunications and wireless-communications are usedinterchangeably hereinafter.

Wireless-network providers generally wish to limit or decrease theamount of roaming that subscribers incur, because the provider does notwant to pay another provider for usage of the other's network. This isespecially true where roaming occurs within an area in which theprovider has attempted to make service available. A user having asubscription to a home network may roam when, for example and notlimitation, the user's mobile device cannot find a home-network signal,a home-network signal is weak or intermittent, or the user's mobiledevice does not properly search for a home-network signal. Ahome-network signal might be weak or not found even within a servicearea of a home-network antenna where for example, a structure, building,or feature of the landscape blocks the signal. Additionally, othersignals or energies may interfere with the signal, or the number ofconnections being serviced by an antenna may decrease the size of anantenna's service area, among others.

A mobile device, such as that described above, may be any wirelessphone, cellular phone, personal digital assistant (PDA), BlackBerry®device, wireless enabled media player, or other device configured tocommunicate over a wireless network. Such communication may be voice,data, image, video, or other type of data and may utilize services andprotocols to enable short message service (SMS), text messaging, email,packet switching for Internet access, and multimedia messaging service(MMS), among others.

A wireless network may comprise any wireless-communications networkconfigured to transmit and receive wireless signals to one or moremobile devices. Communications over the wireless network may becompleted by any available standards or protocols including GlobalSystem for Mobile communications (GSM), Universal MobileTelecommunications System (UMTS) Third Generation (3G), PersonalCommunications Service (PCS), or Ultra Mobile Broadband (UMB), amongothers.

Further, the wireless network antenna may communicate to mobile devicesin any available manner, such as for example simplex (or half-duplex)mode in which the communications travel both from the mobile device toan antenna or from the antenna to the mobile device, but only in onedirection at a time. The communications may also utilize full-duplexmode in which communication travels in both directions at one time overone or more channels.

With reference initially to FIG. 1, a wireless-network environment 100suitable for use in implementations of embodiments of the invention isdescribed. The wireless-network environment 100 may comprise anygeographic area in which wireless-network communications are provided.The environment 100 includes a plurality of home-network towers 102,104, 106, and 108 as well as a plurality of roaming-network towers 102,110 and 112. A home-network tower 102, 104, 106, and 108 comprises atower having one or more wireless network antennas mounted thereon, butmay also comprise any location at which a wireless network antenna for ahome network is located. Such locations may include buildings,skyscrapers, bridges, church steeples, mountains, and hillsides, amongother structures on which an antenna may be mounted.

Similarly, a roaming-network tower 102, 110, and 112 comprises a towerhaving one or more roaming-network antennas mounted thereon, but mayalso comprise any other structure described above for home-networktowers 102-108. Additionally, as depicted by home-network tower 102 androaming-network tower 102, antennas for more than one network can bemounted on a single tower or at a single location.

Each home-network tower 102-108 has three antennas mounted thereon thateach designate a sector A, B, or C about the tower. Each roaming-networktower 102, 110-112 also has three antennas mounted thereon that eachdesignate a sector X, Y, or Z. In embodiments, a home-network tower or aroaming-network tower may have more or fewer than three antennas mountedthereon. The antennas comprise transmitters, receivers, transceivers, orany other available antenna technology for transmitting and receivingradio frequency (RF) signals or any other signal employable in awireless network. The antennas, and any corresponding subsystems, mayoperate on single or multiple channels, may be trunked, multiplexed, orutilize any available systems, protocols, or logic necessary forproviding wireless network communications.

With additional reference to FIG. 2, illustrating a wireless networkcommunications tower 202, sectors 204, 206, and 208, each generallydepict the direction in which a corresponding antenna is aimed. Themounting of the antennas on the tower 202 and RF shielding around theantennas can be used to aim and adjust the size and location of an areaserved by an antenna, among other methods. The service area 210 of anantenna may be viewed generally as extending radially outward from thepie shaped wedge depicting the sector 204. In practice, the RF energyfrom the antenna 102 extends in a more ambiguous form, as generallydepicted by a service area 212, and may change, grow, or retract as moreor fewer callers connect thereto.

With reference now to FIG. 3A, a graphical representation of a map 300depicting a home-network coverage area of a wireless-networkcommunications system is described in accordance with an embodiment ofthe invention. The home-network coverage area map 300 indicates thelocation of a plurality of home-network cell sites 302 and 304 within ahome-network coverage area 306. The home-network cell sites 302 and 304each utilize three antennas, as described above. Each antenna designatesa cell sector 308 which is depicted in the home-network coverage areamap 300 by a pie shaped wedge at each home-network cell site 302 and304. The service area of each antenna or cell sector 308 may generallybe described as extending radially outward in the direction and shape ofthe pie shaped wedge by which it is depicted. As described above withrespect to FIG. 2, in practice the shape of the service area may not beidentical to that indicated by the pie shape, but such will be assumedhere for sake of clarity and illustration. The home-network cell sites302 and 304 are differentiated only by their location in proximity to ahome-network coverage area border 310. The home-network cell sites 302are located interior to the home-network coverage area 306 while thehome-network cell sites 304 are located along the home-network coveragearea border 310.

The home-network coverage area border 310 generally indicates theoutermost edge of a geographic area in which wireless communications ofthe home network are available under standard conditions and using astandard mobile device. The home-network coverage area border 310 isdepicted by a solid line in FIG. 3A, but might be more aptly describedas being grey or fuzzy, because in practice the line may expand orretract with changing conditions in the environment and usage of thehome network's systems.

One or more cell sectors 308 at the cell sites 304 are designated asroaming border sectors 312. A roaming border sector 312 is a cell sector308 that has a service area (such as the service area 210 or 212 asshown in FIG. 2) that falls along or makes up the home-network coveragearea border 310. The roaming border sectors 312 are only distinguishablefrom cell sectors 308 by the location of their service area and by asystem-parameters message that is broadcast therefrom, as will bedescribed in detail below. In another embodiment, cell sites 304 aredesignated as roaming border sites such that each of the one or morecell sectors at each cell site 304 is designated as a roaming bordercell sector 312.

One or more coverage gaps 314 are found within the home-network coveragearea 306. A coverage gap 314 indicates an area within the home-networkcoverage area 306 in which a home-network signal is not available. Thesignal availability may be dynamic in that the signal may be availableat some times and not at others due to factors such as for example andnot limitation, weather conditions, other environmental conditions,home-network usage conditions, or a combination of such factors.Alternatively, a coverage gap 314 may be more permanent where, forexample the gap is a result of a physical feature such as a mountain orbuilding blocking a home network's signal or where the coverage gap 314is out of range of all available home-network cell sites 302 and 304.

One or more cell sectors 316 have service areas that border one or morecoverage gaps 314. Such cell sectors 316 are not designated as roamingborder cell sectors 312, because they are not located along thehome-network coverage area border 310 and a home-network provider doesnot wish to enable roaming within the service area of the cell sector316. In an embodiment, one or more cell sectors 316 are designated asroaming border sectors.

With additional reference to FIG. 3B, a graphical representation of amap 318 depicting a roaming-network coverage area 320 of awireless-network communications system according to an embodiment of theinvention. The roaming-network coverage area map 318 depicts the samegeographic location as the home-network coverage area map 300 describedabove. The roaming-network coverage map 318 includes a roaming-networkcoverage area 320 delineated by a roaming-network coverage area border322. A number of roaming-network cell sites 324 are located within theroaming-network coverage area 320. The roaming-network generally, andthe roaming-network cell sites 320 utilize and comprise anywireless-communications technologies, antennas, configurations, or othercharacteristics as described above for the home network. Further, asingle roaming network is described herein for sake of clarity, butthere may be more than one roaming network providing service to thegeographic region depicted in FIGS. 3A and B.

With additional reference to FIG. 3C, an illustration of a combinedcoverage area map 326 is described according to an embodiment of theinvention. The combined coverage map 326 overlays FIG. 3A on FIG. 3B toillustrate the overlap and interaction of the home-network coverage area306 and its components with that of the roaming-network coverage area320 and its associated components. As shown in FIG. 3C, an overlappingarea 328 occurs where both the home network and the roaming networkprovide service and a roaming-network only area 330 and a home-networkonly area 332 occur where the networks do not overlap.

Referring now to FIG. 4, a flow diagram depicting a method 400 to enablea wireless-telecommunications network to control a way that a mobiledevice selectively initiates communications with one of a home networkversus a second network is described according to an embodiment of theinvention. At 402, one or more home-network cell sites along theboundary of a home-network (such as home-network cell sites 304) orroaming-border cell sectors (such as roaming-border cell sectors 312)are used to define the border of a home-network coverage area (such asthe home-network coverage area 306). A parameter is communicated to amobile device from the home-network cell sites or roaming-border cellsectors, at 404. The parameter is received by the mobile device while inan idle mode. In idle mode the mobile device is not in use for voice ordata communications, but may maintain a connection or periodicallydetermine if a connection is available with a wireless-communicationssystem. In another embodiment, the mobile device may be in an activemode for voice and/or data communications in which voice and/or datatransmissions are actively sent and received.

The communicated parameter takes on a value that is useable by themobile device to determine whether the mobile device is permitted toconnect to a roaming-network cell site as will be described more fullybelow. In an embodiment, the parameter comprises a control logic flagthat can be set/turned on, or un-set/turned off. The parameter mightutilize a digital bit to indicate whether the flag is set or un-set. Theparameter value is communicated by the home-network system to the mobiledevice by any available method, such as for example, as a bit in adigital signal, as part of a carrier wave signal, or by another methodas described above. In an embodiment, the parameter value iscommunicated to the mobile device in a system-parameters message. Theparameter value may be amended to current system-parameters messages byutilizing available fields or by reformatting the system-parametersmessage to add additional fields. The system-parameters message isbroadcast over a paging channel or over any other available channel orfrequency.

As described above, the parameter takes on a value indicating whetherthe mobile device is permitted to roam, at 406. The parameter takes on afirst value when the home-network system from which it is broadcast is anot a roaming-border system, such as a home-network cell site 302. Theparameter takes on a second value when the home-network system fromwhich it is broadcast is a roaming-border system, such as a home-networkcell site 304 or a roaming border sector 312. As described previously,any home-network cell site may be designated as a roaming-border cellsite by a home-network provider. In an alternative embodiment, a mobiledevice may determine whether a home-network system is a roaming-bordersystem by first receiving identifying information from the home-networksystem in a system-parameters message such as network identification(NID), a system identification (SID), and a radio frequency (RF)channel. The identifying information may then be compared to stored datathat is useable to identify the communicating system.

In an embodiment, the communicated parameter value is stored on themobile device. The parameter value is stored until a new parameter valueis received, at which point the initial parameter value is overwrittenwith the latter parameter value. A new parameter value is received whena mobile device initiates a new connection to a home-network system. Amobile device may initiate a new connection when the mobile device isinitially turned on, when it loses a connection with awireless-communications network system, or when it declares system loss,among others. A mobile device may declare system loss when the mobiledevice fails to receive a number of messages from awireless-communications network system. The home-network systemcommunicates the new parameter value to the mobile device and theprevious parameter value is overwritten. The new parameter value may bethe same or different from the previous parameter value. In anembodiment, roaming-network systems do not broadcast a parameter value.In another embodiment, roaming-network systems do broadcast a parametervalue, but only parameter values communicated from a home-network systemare used and/or stored by a mobile device.

A mobile device having stored a first value for the parameter isrestricted to use of home-network systems to connect to awireless-communications network. Thus, when the mobile device loses aconnection with a wireless-communications system or declares system lossthe mobile device is only authorized to initiate a new connection with ahome-network system. If the mobile device detects a signal from ahome-network system it may connect thereto, but if no home-networksignal is detected then the mobile device is rendered out of serviceuntil a home-network system is detected. The mobile device maycontinually or periodically check for signals from home-network systemsto which it may connect. Further, even if the mobile device is able todetect a roaming-network system the mobile device will not initiate aconnection thereto. In an embodiment, the mobile device is authorized toconnect to any available wireless-communications network system foremergency or “911” calls regardless of the parameter value.

A mobile device having stored a second value for the parameter isenabled to connect to either a home-network system or a roaming-networksystem. Thus, when the mobile device loses a connection with awireless-communications system or declares system loss the mobile devicedetects available wireless-communications network systems and mayconnect to home-network or roaming-network systems. In an embodiment,the mobile device is provided with a database describing availablewireless-communications systems to which the mobile device is authorizedto connect, both on the home-network and on one or moreroaming-networks. The database may be prioritized such that home-networksystems have priority over roaming-network systems. Thus, although themobile device in enabled to connect to a roaming-network system, if ahome-network system is detected the mobile device will preferentiallyconnect to the home-network system. The mobile device will only connectto a roaming-network system when no home-network system is detected.

In an embodiment, the database is a preferred roaming list. A preferredroaming list includes a prioritized listing of NIDs, SIDs, and RFchannels on which various home-network and roaming-network systemsoperate, among other data items. An NID, SID, and a channel identifierare communicated to the mobile device from a wireless-communicationsnetwork system on a paging channel and the NID, SID, and channelidentifier are compared to the preferred roaming list to determine ifthe mobile device is authorized to connect to the broadcasting system.

In one embodiment, a mobile device attempting to connect to awireless-communications system first determines the stored parametervalue. If the parameter has the first value, the mobile device thensearches for home-network systems only. Conversely, if the parameter hasthe second value the device searches for home-network androaming-network systems based on their priority as defined by apreferred roaming list. In another embodiment, the mobile device firstsearches for available home-network systems and if none are found, thedevice then checks the stored parameter value to determine whether it isenabled to use roaming-network systems.

With additional reference to FIG. 5 a graphical representation of a map500 depicts a roaming-enabled zone 502 along a border of a home-networkcoverage area 306 of a wireless-network communications system accordingto an embodiment of the invention. The roaming-enabled zone 502generally depicts the service areas of a number of roaming bordersectors 312. In an embodiment, the roaming-enabled zone 502 depicts theservice area of a number of home-network cell sites 304. As such, amobile device located within the roaming-enabled zone 502 attempting toinitiate a new connection with a home-network cell site 304 will receivea second parameter value communicated from a roaming border sector 312thereby enabling roaming of the mobile device. The map 500 also depictsa roaming-restricted zone 504 and a roaming zone 506. A mobile devicewithin the roaming-restricted zone 504 will receive a first parametervalue from home-network cell sites 302 and from cell sectors 313 ofhome-network cells sites 304 that are not designated as roaming bordersectors 312. Conversely, a mobile device in the roaming zone 506 willonly detect one or more roaming-network cell sites 508 or 510 and willnot receive a parameter value therefrom. In an embodiment, a mobiledevice might receive a parameter value from a roaming-network cell site508 or 510, but such a parameter value is discarded.

For example, assume a user is initially located within theroaming-restricted zone 504, such as at point A. A first parameter valueis communicated to and stored on the user's mobile device. Thus, theuser's mobile device is restricted to use of a home-network and can notroam. If the user moves into the roaming-enabled zone 502, such as nearpoint B, and the user's mobile device loses connection with ahome-network cell site 302, the mobile device will attempt to initiate anew connection. The first parameter value is still stored on the mobiledevice, thus the mobile device can only connect to a home-networksystem, such as a home-network system 304 that serves the area of theroaming-enabled zone 502. Upon detecting a signal from a home-networkcell site 304 or a roaming border sector 312 thereof, the secondparameter value is communicated to the mobile device in asystem-parameters message along with the NID, SID, and a channelidentifier, among other information. The second parameter value isstored on the mobile device and overwrites the previously stored firstparameter value.

As such, the mobile device is connected to a home-network cell site 304via a roaming border sector 312 and has a second parameter value storedin memory. If the user then moves into the roaming zone 506, such as topoints C or D, or declares system loss while remaining in theroaming-enabled zone 502 the mobile device can connect to either ahome-network system, such as the home-network cell sites 302 and 304, ora roaming-network system, such as the roaming-network cell sites 508 or510. When initiating a new connection the mobile device will follow theprioritized listing of home and roaming-network systems provided in thepreferred roaming list. Therefore, the mobile device will preferentiallyconnect to an available home-network system over a roaming-networksystem. If no home-network system is available, such as within theroaming zone 506 the mobile device will connect to a roaming-networksystem if one is available.

While within the roaming zone 506 the mobile device will not receive aparameter value, because the parameter value is only communicated via ahome-network system. Thus, the second parameter value is maintained inthe mobile device's memory. Further, while in the roaming-enabled zone502 the mobile device will only receive the second parameter value fromthe home-network cell sites 304 servicing that area, and thus the secondparameter value will be maintained in the mobile device's memory.Therefore, while in either the roaming zone 506 or the roaming-enabledzone 502, roaming is enabled for the mobile device.

Once the mobile device re-enters the roaming-restricted zone 504 andinitiates communication with a home-network cell site 302 the firstparameter value is communicated to the mobile device and the secondparameter value is overwritten with the first parameter value. In orderfor the mobile device to again be enabled to roam it must connect to ahome-network cell site 304 and the second parameter value must becommunicated to the mobile device and stored in memory prior toinitiating a connection to a roaming-network system. In anotherembodiment, an override logic is provide for a mobile device that isinitially powered on within the roaming zone 506 and has the firstparameter value stored in memory, such that roaming may be enabled forthe mobile device.

Returning to FIG. 3C, assume a mobile device located at point X islocated within a coverage gap 314 and therefore loses connection to ahome-network cell site 302 or 304. Within the coverage gap 314 themobile device is unable to detect or connect to a home network system.Further, the mobile device is restricted to use only home-networksystems because the first parameter value is stored on the mobiledevice. Thus, the mobile device is rendered out of service while locatedwithin the coverage gap 314. Such is true even though the location ofpoint X is within the service area of one or more roaming-network cellsites 324. A home-network provider might designate a cell sector 316 ofa home-network cell site 302 or 304 located in close proximity to thecoverage gap 314 as a roaming border sector in order to enable roamingin such a location if such is desired.

A home-network provider may not wish to enable roaming in cell sectors316 around a coverage gap 314, because the loss of service at thecoverage gap 314 may be very brief or may not affect a significantportion of subscribers, among other reasons. For example, if thecoverage gap 314 were in an area that was not heavily traveled bysubscribers, such as a mountain top, or an industrial site then it maynot be cost effective to enable roaming throughout the entire servicearea of the cell sector 316 in order to provide coverage (roamingcoverage) within the coverage gap 314. Conversely, the coverage gap 314may lie in a heavily traveled area such as around an interstate. In sucha location a user may be only briefly out of service and may neverbecome aware that service was lost due to the very short time that theywere within the coverage gap 314. Thus, again a home-network providermay not wish to enable roaming throughout the entire service area of acell sector 316 to provide coverage (roaming coverage) to the area ofthe coverage gap 314.

Referring now to FIG. 6 a block diagram depicting a roaming controlsystem 600 for controlling a way that a mobile device selectivelyinitiates communications with one of a home network versus a secondnetwork is described according to an embodiment of the invention. Theroaming control system 600 includes a parameter-receiving component 602,a system-identifying component 604, and a connection-enabling component606. The parameter receiving component 602 is configured to receive aparameter value from a wireless communications network system, such as ahome-network system or a home-network cell site 302 or 304. Theparameter takes on a first value indicating that a mobile device is notpermitted to roam on a roaming network, or the parameter takes on asecond value indicating that the mobile device is permitted to roam on aroaming network. In an embodiment, the first value is received from anon-roaming border system and the second parameter value is receivedfrom a roaming border system, as described previously. The mobile devicemay also store the parameter value in memory and such storage overwritesany previously stored parameter value.

The system-identifying component 604 receives identification data from ahome network and roaming networks. In an embodiment, the identificationdata includes an SID, an NID, and an RF channel, among other datatransmitted by the home and roaming networks. In another embodiment, thedata is received on a paging channel. The system-identifying component604 compares the received identification data to known identificationdata to identify the communicating home-network or roaming-networksystem. The known identification data may be stored in a database andmay identify home-network and roaming-network systems to which themobile device is authorized to connect. Further, the knownidentification data might also prioritize the home and roaming-networksystems by an order in which a mobile device is to attempt to connectthereto.

Upon attempting to initiate a connection to a wireless-communicationssystem the connection-enabling component 606 is configure to prevent themobile device from communicating with a roaming network when the firstparameter value has been received and to enable communication with aroaming network when the second parameter value has been received.

In an embodiment, the connection-enabling component 606 identifies aparameter value stored in memory. The connection-enabling component 606also enables the mobile device to connect to a roaming network when thesecond parameter value is stored in memory. Conversely, theconnection-enabling component 606 prevents a connection to aroaming-network system when the first parameter value is stored. Inanother embodiment, a mobile device is always enabled to connect to ahome-network system without interaction or authorization by theconnection-enabling component 606.

With reference now to FIG. 7, a flow diagram depicting a method 700 toenable a wireless-telecommunications network to perform a method ofcontrolling a way that a mobile device selectively initiatescommunications with one of a home network versus a second network isdescribed according to an embodiment of the invention. Initially, apreferred roaming list is provided to a mobile device, at 702. Thepreferred roaming list includes prioritized list of a number ofhome-network cell sectors (such as the roaming-border sectors 312 andcell sectors 308) as well as a number of roaming-network sectors or cellsites (such as the roaming-network cell site 324) that a mobile deviceis authorized to use. The preferred roaming also includes NIDs, SIDs,and channels for each of the cell sites or sectors. The preferredroaming list may be provided to the mobile device only once, such asupon initiation of a service subscription for the device or may becontinuously or periodically updated. At 704, a parameter value iscommunicated in a system-parameters message from a home-network cellsector, such as a cell sector 308 or a roaming border sector 312, to themobile device. As described above, the parameter has a first value whenthe communicating cell sector is a non-roaming border sector, such as acell sector 308, and has a second value when the communicating cellsector is a roaming-border sector, such as a roaming-border sector 312.

At 706, the flow diagram diverges into two paths based on whether theparameter value was communicated from a non-roaming border sector or aroaming-border sector (e.g. has a first or second value). In anembodiment, the parameter value is stored in memory on the mobile deviceor the parameter value might be stored remotely in a memory structurenot contained within the mobile device. The stored parameter valueoverwrites any previously stored parameter value. At 708, a mobiledevice has received a first parameter value and is restricted to use ofhome-network cell sectors. At 710, a mobile device, having received thesecond parameter value, is enabled to use either home or roaming-networkcell sectors. As such, the mobile device selectively initiatescommunication with a home or roaming-network cell sector based on apriority given to the sectors in the preferred roaming list.

In another embodiment, two separate parameters, a voice parameter and adata parameter, each taking on one of two values are communicated from ahome-network system to a mobile device. The voice parameter takes oneither a first or a second value and is used to control roaming of themobile device for voice communications. The data parameter also takes oneither a first or a second value and is used to control roaming of themobile device for data communications. As described above, the voice anddata parameters have a first value when the parameters are communicatedfrom a non-roaming border system and a second value when communicatedfrom a roaming border system.

Thus, for example, where a network provider finds it desirable to enableroaming for voice communications in an area, but not data communicationssuch might be achieved by designating cell sectors as roaming bordersectors for voice communications. As such, the designated cell sectorwould communicate a second value for the voice parameter (enablingroaming for voice communications) and a first value for the dataparameter (restricting roaming for data communications), among othervariations.

From the foregoing, it will be seen that this invention is one welladapted to attain all the ends and objects hereinabove set forthtogether with other advantages which are obvious and which are inherentto the structure.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of theclaims.

Since many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

1. One or more non-transitory computer-readable media havingcomputer-executable instructions embodied thereon that, when executed,enable a wireless-telecommunications network to perform a method ofcontrolling a way that a mobile device selectively initiatescommunications with one of a home network versus a second network, themethod comprising: utilizing a plurality of roaming-border components todefine a border of the home network to which the mobile device issubscribed, each roaming-border component providing signal coverage thatcollectively defines the border of the home network; and communicating,from a given roaming-border component to the mobile device, a parameterhaving a first value indicating that the mobile device is authorized toroam to a second network to which the mobile device is not subscribed;and communicating, from a non-roaming-border component of the homenetwork, the parameter having a second value indicating that the mobiledevice is not authorized to roam to the second network even though thesecond network is available to the mobile device and the second networkis permitted to provide roaming service to the mobile device, whereinauthorization of the mobile device to roam to the second network isgoverned by a most recently received value of the parameter, the mostrecently received value comprising either the first or the second value,wherein the plurality of roaming-border components are distinguishedfrom the non-roaming-border component by a location of a respectiveservice area and by a respective value of the parameter communicated. 2.The computer-readable media of claim 1, wherein the roaming-bordercomponents are one or more of a component of a cell sector, a celltower, an antenna, and a base station.
 3. The computer-readable media ofclaim 1, wherein the roaming-border components and the non-roamingborder components broadcast a system-parameters message on a pagingchannel, and wherein the system-parameters message includes theparameter.
 4. The computer-readable media of claim 3, wherein the mobiledevice receives the system-parameters message each time it initiatescommunication with a different roaming-border component or non-roamingborder component.
 5. The computer-readable media of claim 4, wherein themobile device is in an idle mode.
 6. The computer-readable media ofclaim 1, wherein the parameter has the first value indicating that themobile device is permitted to roam to the second network, and whereinthe mobile device selectively initiates communications with one of thehome network or the second network based on a priority.